1. Field of the Present Invention
The present invention relates to an actuating device for machine elements that are subject to wear play, and in particular, an actuating device for brakes of railborne vehicles.
2. Description of the Related Art
Clutches and brakes are machine elements subject to wear play. Machine elements of this kind are used for the transmission of driving forces and braking forces in railborne vehicles. Clutch facings and brake linings which withstand high thermal stresses and which enable desirable transmission of force are used for interrupting and stopping the transmission of force. These facings and linings are subject to wear which gradually causes increasing amount of play between the facings and linings. Adjusting devices are known in the art for compensating for this wear play.
EP 0 174 690, for example, discloses a generic adjusting device having an adjusting nut/spindle assembly which compensates for wear play in brakes. This adjusting device has a control sleeve which is acted upon by spring force so as to prevent, by means of a first coupling, an adjusting nut from performing a longitudinal displacement, and thus a readjustment, of the piston spindle through a rotating movement. After traveling a predetermined play path, the first coupling is disengaged by the displacement of a piston rod over a determined path, so that the adjustment of the play path can be increased corresponding to the amount of lining wear. A further forward movement of the piston engages a second coupling, whereupon the displacement of the adjusting nut on the spindle is halted. This mechanism for coupling and uncoupling the adjusting nut is disadvantageously complicated and expensive to manufacture. However, the use of the basic adjusting nut/spindle principle for adjustment is a quite robust solution which has proven successful in practice.
DE-OS 22 01 082 discloses a generic adjustment device for railborne vehicle brakes in connection with a piston-cylinder unit for brake actuation and with a brake linkage for transmission of braking force.
In the known generic adjusting devices, adjustment of the adjusting nut/spindle assembly for play compensation is only possible during load alternation by means of a coupling process which disadvantageously causes wear. Another problem with known adjusting devices is that there is a high consumption of compressed air due to the long cylinder strokes required for operating the adjusting mechanism.